The present invention relates to a stator of a rotary machine and particularly to an insulating bobbin fitted on a stator core of the stator for winding a stator winding on the stator core.
A rotary machine consists of a stator fixedly disposed inside a casing and a cylindrical rotor installed on a rotating shaft to rotate together therewith. The stator includes a hollow, cylindrical stator core and a stator winding, in which the stator core has a tooth portion (pole tooth portion) on which an insulation bobbin is fitted and the stator winding is wound around the tooth portion by way of the insulating bobbin.
Herein, the insulating bobbin has a coil wound portion, an inner flange portion and an outer flange portion. The coil wound portion is in the form of a rectangular frame and fitted on the tooth portion having a rectangular cross section. The inner flange portion and the outer flange portion are formed integral with the coil wound portion and in such a way as to extend along the inner and outer edges of the coil wound portion, respectively. The coil wound portion has a slot side section, a coil end section and a corner section. The slot side section forms a winding slot for winding thereon a stator winding while insulating the same. At the coil end section is disposed an end portion of the stator winding. The corner section connects between the slot side section and the coil end section. At the corner section, the insulating bobbin and the stator winding are brought into contact with each other strongly, by the tension of the stator winding caused at the time of its winding. Due to this, the insulation coating of the stator winding or the insulating bobbin may be damaged by being pushed by the stator winding. As a result, there may possibly occur an insulation failure of the stator winding or breakage of the inner flange portion of the insulation bobbin, which starts at the place where the insulation bobbin is damaged by a large stress applied thereto at the time of a magnetizing process.
Further, since the slot side section of the insulating bobbin is generally thin, the corner section is liable to be cracked to cause an insulation failure of the insulating bobbin.
An example of a related technique for solving such a problem is disclosed by a Japanese Patent No. 3679305 titled “Cooling Medium Compressor”. In the cooling medium compressor, it is aimed to relieve the stress which is caused due to bending of a stator winding and applied to a corner section of a coil wound portion of a direct-wound type insulating bobbin. To this end, it is proposed to round the corner section of the coil wound portion so that the rounded corner section has a curved surface shape formed by a circular arc of a radius in the range from ½ to 4 times of the diameter of the stator winding wire. By such rounding, it becomes possible to attain improved protection of the insulation layer of the stator winding and the insulating bobbin against damage, and it becomes possible to prevent occurrence of an insulation failure and breakage of the insulating bobbin at the time of magnetization.